How do i change the colour of sidebar search box background

Hi there,

the color is added using CSS.
Go to Customizer > Additional CSS and look for:

.sidebar .widget:first-child, .sidebar .widget:first-child .widget-title {
    background-color: #83b0de;
    color: #fff;
}

You can either delete that CSS if you want it to match the other widget colors.
Or change the #hex colors to suit your need

Thanks it worked!

Glad to hear that!